The asphalt-concrete used as a major component of an asphalt pavement typically consists of a mixture of about 5% asphalt and 95% rock aggregate by weight. Rutting and stripping are two major distresses which occur in pavements constructed of hot mix asphalt (HMA) or warm mix asphalt (WMA) pavement. Rutting is the formation of depressions in the pavement in the direction of traffic flow under the influence of a moving wheel load. Stripping is the physical separation of asphalt cement from aggregate and asphalt coated aggregates from one another.
“Wheel-tracking” tests, in which a loaded wheel repeatedly travels across pavement or laboratory prepared samples or specimens to simulate the action of traffic, have been utilized to predict the rutting and/or stripping potential of the HMA pavement samples. One wheel-tracking test uses the Hamburg wheel-tracking device, developed by Helmut-Wind, Inc. of Hamburg, Germany. In the standard Hamburg test, two HMA specimens are submerged in water maintained at 50° C. (122° F.) and loaded by a wheel with a wheel load of 705 N (158 lbf). The test is performed to a maximum of 20,000 passes of the wheel over the specimen or until a specimen deformation of 20 mm (0.79 in) is recorded.
With known wheel-tracking devices, a heavy loading arm (i.e., one that imparts a wheel load of 705 N or 158 lbf on the specimen) is manually lifted by an operator or by a winch (which an operator must connect prior to the lifting). Also with known devices, an operator lifts a heavy tray with two cylindrical specimens or a slab specimen weighing between 35 and 50 pounds and typically seats the tray on brackets or the like in the water bath without any mechanical assistance.